alleryHow does ionisation energy generally change on moving down a group in the periodic table?
AIncreases
BDecreases
CStays the same
DBecomes zero
Answer & Solution
Correct answer: B. Decreases
1. Down a group the atomic size increases as more shells are added.
2. The valence electrons are farther from the nucleus and loosely bound.
3. Less energy is needed to remove them, so ionisation energy decreases down a group.
Ionisation energy increases across a period, but the question asks about a group.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 8 Periodic Classification of Elements "Ionisation Energy", p.117_
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